Application of Falling Weight Deflectometer in Railway Track to Assess Ballast and Subgrade Conditions

This paper describes an investigation into the applicability of falling weight deflectometer (FWD) for evaluating structural conditions of railroad track substructures. The research study involved six full-scale test sections constructed at the U.S. Army Engineering Research and Development Center facility, each with different combinations of fouled and clean ballast, as well as poor, moderate, and good subgrade conditions. The experimental program focused on investigating the impact of different FWD load plate materials—aluminum, plastic, and rubber, in addition to the original steel—on the measurement repeatability and condition assessment of ballast and subgrade using both centerline and offset geophone sensors. The FWD test results collected from the different substructure conditions were analyzed using statistical methods, including F-tests, T-tests, and analysis of variance, to determine significance of results and any differences in deflections. Results show that the type of loading plate affects primarily the centerline deflection and measurement repeatability. Furthermore, the measured centerline deflections could be used to distinguish between fouled and clean ballast conditions with good subgrades, while the 40 in. (101.6 cm) offset sensor deflection could determine poor, moderate, and good subgrades, regardless of ballast conditions. This research demonstrates the potential of using the FWD as an effective and reliable tool for track substructure assessment in ballasted track and provides insights into the effects of ballast fouling and subgrade quality on track performance.